Flame holder structure for ram jet combustor



Nov. l1, 1958 H, l, wlLsoN 2,859,588

FLM/IE HOLDER STRUCTURE FOR RAM JET COMBUSTOR Filed Dec. 16, 1953 United States Patent O FLAME HOLDER STRUCTURE FOR RAM JET COMBUSTOR Herman I. Wilson, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application December 16, 1953, Serial No. 398,513

2 Claims. (Cl. 60-35.6)

This invention relates generally to combustion apparatus of the jet propulsion type, and specifically to a ram jet combustor, in which fuel is burned in a moving stream of pressurized air, with the resulting products of comA bustion being discharged as a propulsive jet.

This application is a continuation-impart of my copending application Serial No. 321,246, led November 18, 1952, now abandoned.

One of the problems in satisfactory operation of ram jet apparatus under diverse conditions is the maintenance of satisfactory combustion throughout a wide range of overall fuel-air ratios, especially with leaner values. Under certain operating conditions, the lower limit of combustion may be passed easily and the combustion ame may die out; on the other hand, during periods of high fuel consumption when developing high power, localized areas of fuel-air mixture often become too rich for stable combustion or good fuel economy. Some extension of the operable limits of overall fuel-air ratio has been attained in combustion apparatus of the prior art by controlled distribution of fuel through a plurality of fuel supply manifolds each equipped with a number of fuel-emitting nozzles for the impregnation of localized portions of air at local fuel-air mixture ratios which are proper for satisfactorily stable combustion, while permitting variation of the number of nozzles actually in operation to change the overall fuel-air ratio. The extension of combustion limits by this method has the disadvantage of mechanical complexity. The present invention provides combustion apparatus having an improved range of satisfactory combustion while retaining all the advantages of mechanical simplicity.

Therefore, it is an object of the present invention to provide improved air combustion apparatus of the jet propulsion type enabling operation with stable combustion over an increased range of overall fuel-air ratios.

It is another object of the invention to provide combustion apparatus of the aforesaid type which is mechanically simple in structure and which can be easily and inexpensively manufactured.

It is still another object of the invention to provide combustion apparatus of the aforesaid type which is capable of operation with improved economy over a wide range of overall fuel-air ratios.

A further object of the invention is to provide combustion apparatus of the aforesaid type wherein improved mixing of the fuel and air over a wide range of fuel-air ratios is obtained.

These and other objects of the present invention will become apparent from a consideration of the following description taken in conjunction with the accompanying drawings in which Figure 1 is a longitudinal partial cross section of a ram jet apparatus constructed in accordance with the present invention,

Figure la is a partial longitudinal cross section of a modification of the ame holder structure disclosed in Figure 1,

Figure 2 is a cross sectional view taken on line 2-2 of Figure 1, and

Figure 3 is a diagrammatic perspective sectional view of an apparatus similar to Figure 1, wherein a multiple installation of the novel flame holder structure is used.

Briefly, my invention contemplates an improved jet propulsion apparatus having a combustion chamber through which air or an equivalent gas liows, a fuel emitting device for introducing fuel into the iiowing air or gas as a stream or solid narrow cone spray, and a flame holder structure including a fuel impingement or splash plate positioned in the path of the emitted fuel.

Referring to Figures 1, la and 2 of the drawings, a combustion apparatus constructed in accordance with my invention includes a combustion chamber 2 comprising cylindrical wall 4 defining a duct through which air flows in a generally axial direction, indicated by arrows F, at a relatively high velocity during operation of the propulsion engine of which it is a part.

A fuel supply pipe 6, connected to a fuel supply manifold 8, terminates within the combustion chamber in a nozzle 10, of the simplest design, such as a drilled hole, pintle, or soli-d cone type capable of providing a high velocity, narrowly confined stream or spray of fuel.

The nozzle 10 is shown positioned on the longitudinal axis of the combustion chamber 2, and is oriented therein to spray fuel in the same direction as the flowing air stream.

Downstream from the fuel nozzle 10, there is positioned a flame holder structure 12 consisting of a number of individual turbulence producing elements or flame holders 14, joined to each other and to the cylindrical wall by convenient fastening means and depicted as hollow truncated cones oriente-d with their axes parallel to the longitudinal axis of the chamber 2 and concentrically disposed thereabout with closed ends facing upstream and large ends open in the downstream direction. Each individual element 14 of llame holder structure 12 serves the conventional purpose of creating a localized area of turbulence within its open end periphery and a resultant localized low velocity air flow in which stable combustion can be maintained under `conditions when the velocity of air flow through the combustion chamber is much greater than normal llame front propagation velocity during combustion, and when, therefore, in the absence of a ame holder, flame front combustion could not exist.

Although the disclosed llame holder is a preferred embodiment, it should be understood that other flame holder designs may be utilized with this invention.

Concentrically disposed on the axis of the combustion chamber 2 and nested among the flame holders 14, as shown in Figure l, or located slightly upstream of the flame holders, as shown in Figure la, and directly in the path of fuel emitted from the nozzle 10, is an impingement or splash'plate 16, located transversely of the air ow and arranged so that the fuel strikes it directly. The splash plate 16 may have the shape of a disc, as disclosed, or other equivalent surface capable of defleeting the fuel stream from its initial path and dispersing it into the adjacent turbulent air to enable the formation of a combustible fuel-air mixture in the vicinity of the periphery of splash plate 16.

A spark plug or other equivalent positive ignition device shown schematically at 18 is located at a distance sufficiently downstream from the splash plate 16 to allow adequate time for the fuel to mix with the air in satisfactory proportions to form an ignitible mixture. A similar ignition device is used adjacent a flame holder 14 as indicated at 18.

-assasss -In lthe operationofthe above-described combustion apparatus, mwith a .low fuelfiflowrate, correspondinghtona low overall fuel-air ratio, the comparatively low velocity fuel stream emitted from nozzle 10 impinges on the splash plate. 16,:d-isperses,. and undergoes Vatomization.andpa-rtial vaporization in the immediate downstream vicinitygto form a combustible fuel-air: ,mixture whichzis ignitedvby spark plug 18 to initiate combustion. Thus, vatlow.' fuel ow rates, the splashpla teitself creates .-sucient localized turbulence'to serve. as .a flame-holder .upon which the flame front Aresulting from :thefcombustion oftheslow fuel quantity isY more reliablystabilized .than on the vregular flame holders.A 14.

At-.high fuel yflow rates, -thedeecting action vof splash plate 16 serves todisperse .the higher velocityfuekstream overa wider transyersearea within the ,combustion charnber 2. The fuel vis -s ,cattered.throughoutthe. substantially higher velocity airgthenl-iiowing.through thecombustion chamber, which contributes. to Aimproved mixingof each inc rement of f uel V,with sufficient air to`V insurezitscomplete combustion withoutthe-,presenceof localized ,areas,-.,.of rich fuel-air mixtures, ignition being accomplished by the ignition devices.18and 18. Theiflarne frontpresulting from the combustion of fuel thusdispersedacross.the combustion chamber by the detlecting action ,of ,the splash plate 16 stabilizes on the regular flame holders 14.

To those skilled, inthe art, it will be ,obviousv that-the configuration of the flame holder structure of Figure la wouldbe more suitable for operation during periods when high overall fuel-,air ratios exist, because of the wider dispersionof thefuel desired across a transversesection of the faster flowing-pair. Further, it is considered to :be within the range of Vmechanical skill tov have the .position of the splash plate adjustable (not shown) for variable and so more economical employment depending upon the fuel ow rate.

Figure 3 discloses the multiple installation of the ame holder structure of Figure l, the same or similar elements bearing identical numeration. Only one fuel nozzle is shown opposite a splash plate, for clearness of depiction, but in actual operation, each splash plate would be positioned downstream of a corresponding fuel nozzle. vIt should be apparent that the modification of Figure la may also be used in a multiple installation, or that the position of splash plate 16 may be made adjustable.

Thus, it may be seen that there has beenshownand described an improved combustion apparatus of the'ljet propulsion type providing improved fuel dispersion for more complete and efcient combustion of all increments of fueLwitltout localized excessively rich mixtures'V at high overall fuel-air ratios, and providing limproved combustion stability atlow overall fuel-air ratios, which thereby enables economical operation with'stable combustion over any increased range ofoverallY fuel-air ratios.

Obviously many modifications and variations of lthe invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof. For example, the depicted embodiments of the invention, installed fina cylindrical combustion chamber, may serve as one of .-several identical incremental parts of al larger-combustion chamber of annular cross section (not shown), with each increment operating in the same manner and alfording the same advantages as hereinbefore set forth. Therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In combination with a jet-propulsion device of the ram jet type having a combustion chamber, llame holding andf'igniting means therefor comprising ka flamelholder structure mounted in said chamber transverse-tothedirection of air flow therethrough, and ignition means Afor igniting combustible fuel-air mixtures positionedadjacent and downstream said flame holder structure, means for providing fuel to -said combustion-chamber in the direction of air flow therethrough and being located upstream with respect to said flame structure, said structure comprising a plurality of llame holder elementszin .the-.shape of hollow truncated cones with .bases open downstream and a splash plate separate from andsurrounded by said elements and located with respect to said means fory providing fuel for the direct impingement of fuel thereon, whereby said fuel is dispersed over said plate .and :said elements to provide localized combustible fuel-airmixtures in their downstream vicinities.

2. In combination, in a ramjet propulsive ,device having a combustion chamber through which` an air stream is directed, fuel emission `means for injecting fuel into said air stream in `said combustion chamber andinV the same-y direction of flow as lthat of said airstream, fuel impingement means disposed in said chamber transverse tothe flow ofsaid air stream and in the path of saidfuel for directjimpingement thereon thereby-creating a localized area of turbulence in said air stream and dispersing fuel transversely of said airstream in said localizedarea of turbulenceto form .a localized combustible fuel-,air mixture, means for igniting said fuel-airmixture to produce a flame front being located downstream of said splash plate, and flame holder means separate from and spacedin surrounding relationship to said. fuel .impingement means for stabilizing said ame front adjacent-said fuel impingement means, said ame holder means, cornprising elements in the shape ofhollow truncated cones with open bases located so that the trailing edges ofsaid flame holder means are downstream of said fuelv impingementl means.

References Cited in the le of this patent UNITED STATES PATENTS .2,508,420 Redding Maya-23,1950 2,529,506 Lloyd et al Nov. 13,1950 ,2,563,024 `Goddard Aug. 7, l1551 2,632,300 4Brzozowski Mar. 24, 1953 2,651,178 Williams Sept. 8, 19.53 ,2,657,532 :Reid et al. Nov.f.3,;1953 2,722,100 Goddard Nov. l, 1955 

